1. Field of the Invention
The present invention relates to a slidable constant velocity universal joint for use in a power transmission system for automobiles, various industrial machines or the like and, more specifically, to a slidable constant velocity universal joint which is capable of transmitting rotary motion at constant velocity even when driving and driven shafts to be joined together are at an angle (operating angle) with respect to each other and which allows a relative axial movement between driving and driven shafts.
2. Description of the Related Art
As shown in FIG. 5, for example, in the power transmission system of a conventional vehicle such as an agricultural tractor, two power transmission shafts 120 and 130 and both ends of a propeller shaft 150 arranged between them are operationally connected with each other via cross joints 100a and 100b, respectively (see, for example, JP05-178105A and JP2003-300422A). The mounting structure for the cross joints and the power transmission shafts will be described with reference to FIG. 5; in the case of one cross joint 100a (the one on the left-hand side as seen in the drawing), a cylindrical portion 101a with a female spline groove formed therein is fitted onto a spline shaft 121 of the mating power transmission shaft 120 with a male spline groove formed therein, with a bolt 105 being engaged with a recess 122 formed in the outer periphery of the spline shaft 121.
In the case of the other cross joint 100b (the one on the right-hand side as seen in the drawing), a cylindrical portion 101b with a female spline groove formed therein is fitted onto a spline shaft 131 of the mating power transmission shaft 130 with a male spline groove formed therein. That is, the right-hand cross joint 100b is axially slidable with respect to the power transmission shaft 130, whereby, even if the relative position between the two power transmission shafts is changed due to engine vibration or the like, it is possible to absorb any glitch at each connecting portion due to the relative positional deviation. As a result, the fit-engagement between the members is properly maintained, and rotational torque is transmitted in a satisfactory manner.
However, in the conventional example shown in FIG. 5, the right-hand cross joint 100b is fit-engaged with the spline shaft 131 so as to be slidable, so that wear occurs at the fit-engagement portion. Further, the left-hand cross joint 100a has to be fixed to the power transmission shaft 120 by the bolt 105, and the mounting operation involved is problematic.
To solve the above-mentioned problems, a slidable constant velocity universal joint in which, as shown in FIG. 6, coil springs 201 are provided between the ends of a shaft 200 and receiving members 205 arranged inside outer rings 202 has been proposed (see Patent Application No. JP 2008-115943 A). Due to the use of the coil springs 201, the distance between the slidable constant velocity universal joints at both ends is variable, whereby the slidable constant velocity universal joints can be easily mounted to two power transmission members 203 spaced apart from each other by a predetermined interval.
In the slidable constant velocity universal joint shown in FIG. 6, when the shaft 200 assumes an operating angle, cap members 204 provided at the forward ends of the coil springs 201 slide on the receiving members 205 arranged inside the outer rings 202. That is, the coil springs 201 are also inclined in conformity with the shaft 200, so that if the sliding motion of the cap members 204 relative to the receiving members 205 is not effected smoothly, the coil springs 201 may be bent, making it impossible to maintain a stable attitude. This may lead to deterioration in stability in torque transmission.